ABSTRACT The Minjur Formation crops out along the eastern rim of the Arabian shield and consists of alternating sandstone and shales with minor carbonates. Informally subdivided into lower and upper units, the Minjur Formation records depositional environments ranging from alluvial to marginal marine with tidally influenced channels. The stacking patterns reflect delta or shoreline progradation and retrogradation, recording an overall coarsening upward character. In outcrop, the Minjur Formation was dated as Norian by conodonts near the base. In the subsurface, palynology has established a fourfold biostratigraphic subdivision extending from latest Carnian–early Norian to latest Rhaetian–Pliensbachian (Triassic–Early Jurassic). This study improves the understanding of Minjur stratigraphy and presents a depositional model based on surface–subsurface correlation. Subsequent to a period of subaerial exposure in the west, transgression in the early middle Norian was marked by marginal marine environments, with peak marine influence in the mid–late Norian and corresponding to the maximum flooding interval Tr80. This was followed by development of a gently inclined alluvial or coastal plain. An intra-Rhaetian hiatus separates the Lower Minjur Formation from the Upper Minjur Formation (base of TSS AP7[?]), and a variety of depositional environments are represented, including alluvial fans proximally, grading to fluvial to coastal plain and shallow marine environments distally.

ABSTRACT The Sallah Formation crops out in Central Saudi Arabia where it is 30 metres thick. It consists of lagoonal and inter-tidal sediments, including locally a marine fauna, which were deposited during a regional trangression above the Biyadh Sandstone. The formation is unconformably overlain by the continental clastics of the Huraysan Formation. A single ammonite recovered from the Sallah Formation is here conclusively assigned to the top of Lower to base of Upper Aptian Cheloniceras sp. and supports its correlation to the Early Aptian Shu’aiba Formation in the subsurface of eastern Saudi Arabia. The Sallah Formation forms a complete transgressive-regressive sequence and the middle Sallah unit 2 (11 metres thick) contains the maximum flooding surface MFS K80. The Late Aptian, for the most part, is interpreted as a hiatus of non-deposition associated with a major sea-level lowstand in Central Saudi Arabia. The overlying continental Huraysan Formation is correlated to the Nahr Umr Formation of Oman and the United Arab Emirates and Burgan Formation of Kuwait.